optparse.coffee

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```
{repeat} = require './helpers'
```
A simple OptionParser class to parse option flags from the command-line. Use it like so:
```
parser  = new OptionParser switches, helpBanner
options = parser.parse process.argv
```
The first non-option is considered to be the start of the file (and file option) list, and all subsequent arguments are left unparsed.

The coffee command uses an instance of OptionParser to parse its command-line arguments in src/command.coffee.
```
exports.OptionParser = class OptionParser
```

Initialize with a list of valid options, in the form:

[short-flag, long-flag, description]

Along with an optional banner for the usage help.

  constructor: (ruleDeclarations, @banner) ->
    @rules = buildRules ruleDeclarations

Parse the list of arguments, populating an options object with all of the specified options, and return it. Options after the first non-option argument are treated as arguments. options.arguments will be an array containing the remaining arguments. This is a simpler API than many option parsers that allow you to attach callback actions for every flag. Instead, you’re responsible for interpreting the options object.
The CoffeeScript option parser is a little odd; options after the first non-option argument are treated as non-option arguments themselves. Optional arguments are normalized by expanding merged flags into multiple flags. This allows you to have -wl be the same as --watch --lint. Note that executable scripts with a shebang (#!) line should use the line #!/usr/bin/env coffee, or #!/absolute/path/to/coffee, without a -- argument after, because that will fail on Linux (see #3946).
```
    {rules, positional} = normalizeArguments args, @rules.flagDict
    options = {}
```

The argument field is added to the rule instance non-destructively by normalizeArguments.

    for {hasArgument, argument, isList, name} in rules
      if hasArgument
        if isList
          options[name] ?= []
          options[name].push argument
        else
          options[name] = argument
      else
        options[name] = true

    if positional[0] is '--'
      options.doubleDashed = yes
      positional = positional[1..]

    options.arguments = positional
    options

Return the help text for this OptionParser, listing and describing all of the valid options, for --help and such.

  help: ->
    lines = []
    lines.unshift "#{@banner}\n" if @banner
    for rule in @rules.ruleList
      spaces  = 15 - rule.longFlag.length
      spaces  = if spaces > 0 then repeat ' ', spaces else ''
      letPart = if rule.shortFlag then rule.shortFlag + ', ' else '    '
      lines.push '  ' + letPart + rule.longFlag + spaces + rule.description
    "\n#{ lines.join('\n') }\n"

Helpers

Regex matchers for option flags on the command line and their rules.

LONG_FLAG  = /^(--\w[\w\-]*)/
SHORT_FLAG = /^(-\w)$/
MULTI_FLAG = /^-(\w{2,})/

Matches the long flag part of a rule for an option with an argument. Not applied to anything in process.argv.
```
OPTIONAL   = /\[(\w+(\*?))\]/
```

Build and return the list of option rules. If the optional short-flag is unspecified, leave it out by padding with null.

buildRules = (ruleDeclarations) ->
  ruleList = for tuple in ruleDeclarations
    tuple.unshift null if tuple.length < 3
    buildRule tuple...
  flagDict = {}
  for rule in ruleList

shortFlag is null if not provided in the rule.

    for flag in [rule.shortFlag, rule.longFlag] when flag?
      if flagDict[flag]?
        throw new Error "flag #{flag} for switch #{rule.name}
          was already declared for switch #{flagDict[flag].name}"
      flagDict[flag] = rule

  {ruleList, flagDict}

Build a rule from a -o short flag, a --output [DIR] long flag, and the description of what the option does.

buildRule = (shortFlag, longFlag, description) ->
  match     = longFlag.match(OPTIONAL)
  shortFlag = shortFlag?.match(SHORT_FLAG)[1]
  longFlag  = longFlag.match(LONG_FLAG)[1]
  {
    name:         longFlag.replace /^--/, ''
    shortFlag:    shortFlag
    longFlag:     longFlag
    description:  description
    hasArgument:  !!(match and match[1])
    isList:       !!(match and match[2])
  }

normalizeArguments = (args, flagDict) ->
  rules = []
  positional = []
  needsArgOpt = null
  for arg, argIndex in args

If the previous argument given to the script was an option that uses the next command-line argument as its argument, create copy of the option’s rule with an argument field.

    if needsArgOpt?
      withArg = Object.assign {}, needsArgOpt.rule, {argument: arg}
      rules.push withArg
      needsArgOpt = null
      continue

    multiFlags = arg.match(MULTI_FLAG)?[1]
      .split('')
      .map (flagName) -> "-#{flagName}"
    if multiFlags?
      multiOpts = multiFlags.map (flag) ->
        rule = flagDict[flag]
        unless rule?
          throw new Error "unrecognized option #{flag} in multi-flag #{arg}"
        {rule, flag}

Only the last flag in a multi-flag may have an argument.

      [innerOpts..., lastOpt] = multiOpts
      for {rule, flag} in innerOpts
        if rule.hasArgument
          throw new Error "cannot use option #{flag} in multi-flag #{arg} except
          as the last option, because it needs an argument"
        rules.push rule
      if lastOpt.rule.hasArgument
        needsArgOpt = lastOpt
      else
        rules.push lastOpt.rule
    else if ([LONG_FLAG, SHORT_FLAG].some (pat) -> arg.match(pat)?)
      singleRule = flagDict[arg]
      unless singleRule?
        throw new Error "unrecognized option #{arg}"
      if singleRule.hasArgument
        needsArgOpt = {rule: singleRule, flag: arg}
      else
        rules.push singleRule
    else

This is a positional argument.

      positional = args[argIndex..]
      break

  if needsArgOpt?
    throw new Error "value required for #{needsArgOpt.flag}, but it was the last
    argument provided"
  {rules, positional}

Helpers